For years, medical science has administered various gases to patients. Primarily these gases include anesthetics that are administered to patients during surgery, and oxygen or air that is administered to patients either post-operatively, or at other times for therapeutic reasons.
The gas to be administered is typically contained within a sealed container. The sealed container includes an outlet port and a valve for controlling the flow of gas through the outlet port. A breathing circuit is provided for transporting the gas from the outlet port to an element such as a face mask that is in contact with a patient.
Various types of breathing apparatus and circuits have been used in the past.
Richardson and Field U.S. Pat. No. 746,380 discloses a device that was patented in 1903 for administering anesthetics. The Richardson device includes a mouth part and a nose part. The mouth and nose parts are separately connected by means of a bushing or tubular fitting. The device includes a gas receptacle which has a flexible tube at one end, and is secured in place by an elastic band or strap.
A more recent prior art breathing circuit is shown in FIGS. 1 and 2 of Fukunaga U.S. Pat. No. 4,265,235. This illustrated device comprises a typical "circle-type" breathing circuit that includes a source of gas, a conduit extending therefrom, and a carbon dioxide absorber which receives expiratory gas through a conduit. Reprocessed gas moves out of the outlet after having passed through the carbon dioxide absorbing granules. As the reprocessed gas moves out of the outlet, it joins fresh gas from the source, as the fresh gas is arriving through the conduit. The merged gases then pass through the one-way inspiratory valve and the flexible hose into the common inlet-outlet pipe as inspiratory gas to the inlet means, and then to the patient's respiratory system. The expiratory gas is returned through the inlet pipe, but is then passed through the return hose, a one-way expiratory valve, past a reservoir bag and into the carbon dioxide absorber.
One difficulty with circle-type devices such as the prior art device shown in FIGS. 1 and 2 of Fukunaga is that they are cumbersome and inefficient. To overcome the problems of such circle-type systems, UNILIMB systems have been developed wherein an inspiratory tube and an expiratory tube have been designed to be coaxial with each other, so that one (usually the inspiratory tube) fits inside the other (usually the expiratory tube). With such an arrangement, manipulation becomes less complicated, and the surgical theater becomes less cluttered as the anesthesiologist has one less breathing tube to deal with. Examples of such UNILIMB type circuits are shown in Fukunaga U.S. Pat. No. 4,265,235 and Paluch U.S. Pat. No. 4,007,737.
Paluch discloses an anesthesia breathing apparatus which includes concentrically oriented double tubular inhalation and exhalation lines, having one of the tubes positioned interiorly of the other tube. In Paluch, the inhalation (inspiratory) tube is the corrugated inner tube, and the corrugated exhalation (expiratory) tube is disposed exteriorly of the inhalation tube. A fitting is provided at the machine end of the tube and another fitting is provided at the patient end of the device. A face mask is coupled to the fitting at the patient end of the device.
Fukunaga relates to an anesthesia system breathing circuit of the coaxial type. Fukunaga's device includes an inspiratory tube which is disposed interiorly of the expiratory tube. The difference of the diameter of these two tubes is such that a sufficient volume of expiratory air may pass between the outer wall of the inspiratory tube and the inner wall of the expiratory tube. In the Fukunaga device, the outer tube is preferably constructed as a corrugated tube, while the inner tube is preferably extruded of a vinyl type smooth bore material. A first terminal element is provided at one end of the tubes, and a second terminal element is provided at the other end of the tubes.
Although the above discussed devices most likely perform their intended function in a workman-like manner, room for improvement exists. It is therefore one object of the present invention to provide a breathing circuit which improves upon the known coaxial-type breathing circuits by eliminating some of the problems and drawbacks found with prior, known coaxial-type breathing circuit systems.